Check String whether it contains only Latin characters?

Question

Greetings,

I am developing GWT application where user can enter his details in Japanese. But the \'userid\' and \'password\' should only contain English characters(L

Answer 1

I successfully used a combination of the answers of user232624, Joachim Sauer and Tvaroh:

static CharsetEncoder asciiEncoder = Charset.forName("US-ASCII"); // or "ISO-8859-1" for ISO Latin 1

boolean isValid(String input) {    
    return Character.isLetter(ch) && asciiEncoder.canEncode(username);
}